Active control of the pantograph articulated frame to reduce contact force fluctuations in the low frequency range

This paper describes a concept for active pantograph control, aimed at reducing contact force fluctuation in the low frequency range related to the span-passing frequency. This is based on measuring pantograph frame acceleration and compensating its inertia by means of a control force exerted by the pneumatic spring placed at the bottom of the articulated frame. The use of devices currently equipping the pantograph, such as the air spring to raise/lower the pantograph and a servo-valve to regulate the preload, makes the system cheap and feasibly installable on service trains.